Optical brighteners for use with paper



United States PatentOfiice 3,618,287 Patented Jan. 23, 1962 Ditriazyl derivatives of 4,4'-diaminostilbene-2,2-disulionic acid have heretofore been employed for the optical brightening of textiles, paper, etc. In those compounds used for brightening cellulose, the triazine rings are generally substituted by amine groups. With the sized paper materials which are frequently employed today in the manufacture of paper, most of the presently known brighteners-and particularly those with the best brightening action-are bound up with the deficiency, when applied in the so-called size press, that instead of brightening the paper, they impart a dirty green discoloration thereto so that the degree of whiteness is actually reduced. These discolorations are, on the one hand, due to the low pH-about 4.5-5.0on the surface of the paper and, on the other hand, to the a tion of the sizing, which conventionally is carried out with resin milk (Harzmilch") and aluminum sulfate.

A primary object of the present invention is the obviation of this difiicu'ty. According to the invention, this object is achieved by the proviiion of a new group of compounds-derivatives of 44-bis-(2,4-diamino l,3,5- triazyl (6) amino) stilbene 22 disulfonic acid wherein at least one hydrogen atom of at feast one amino group of the triazine rings is replaced by a cyanoalkyl group. These new compounds are valuable brighteners which do not prejudicially exhibit the aforementioned disadvantage of green discoloration of paper in the size press.

The new compounds of the invention are represented by the following formula outs on the triazyl radicals in the general type of compound here involved.

These new compounds I can be prepared by reacting, in any order of succession, 2 mols of cyanuric chloride 5 with:

(a) 1 mol of 4,4-diaminostilbene-2,2'-disulfonic acid or a salt thereof,

(b) 1 to 4 mols of one or more cyanoalkylamines of the formula R R 'NH-(0H CH (JEN wherein R, R and n are as precedingly defined, and

(c) 0 to 3 mols of one or more primary or secondary amines or of ammonia,

the total number of mols in (b)+(c) being four.

The brighteners according to the invention can be symmetrically or unsymmetrically constructed with respect to the X and V groups as well as with respect to the Y and Z groups. In the symmetrical compounds X is the same as V, and Y is the same as Z. In the unsymmetrical compounds, e.g. X may be identical with V, and Y different from Z, or Y may be the same as Z and X different from V, or X, Y, Z and V may be different from each other.

The symmetrical compounds are obtained by condensing, in any desired order of succession, preferably in a solvent and/or in the presence of a dispersing agent in aqueous medium, at 0-10 C. two mols of cyauuric chloride with one mol of 4,4'-diamino:till:en:-2,2'-disulfonic acid or a water-soluble salt thereof, to produce the 4,4- bis (2,4 dichloro 1,3,5 triazyl (6) amino) stilbene-2,2'-disulfonic acid or corresponding salt, and condensing the latter at 20-50 C. wi.h two mols of a base of formula V-H and at 80-100 C. with two mols of a base of formula Y-H or Z-H, in which formulae Y, Z and V have the precedingly indicated significances. The HCl liberated in the condensation is neutralized with wherein each of X, Y and Z is an amino radical which may be identical with V attached by the amino nitrogen to the adjacent triazine ring and wherein each of X, Y and Z may be NH R stands for hydrogen or methyl, R stands for hydrogen, alkyl or hydroxyalkyl or lower alkoxyalkyl (the R alkyl group containifg l to 4 carbon atoms), and n ripresents zero or one. The watersoluble salts of these compounds are also included in the scope of this invention.

The essential and characteristic moiety of compounds I is the group V, wherein R, R and n are as precedingly defined, and the presence of at least one such moiety is indispensible to the desired results. The moieties X, Y and Z, on the other hand, are widely variable and, except as they may be identical with V, have been used as substitualkali, e.g. akali metal hydroxide, alkali metal carbonate,

alkali metal acetate, etc.

Asymmetrical compounds are conveniently prepared by reacting one mol of cyanuric chloride at 0-10 C. with one mol of 4-nitro-4'-aminostilbene-Z,2-disu1fonic acid, at 20-50 C. with one mol of a base of formula X-H- and at 80l00 C. with one mol of a base of formula YH, reducing the nitro group to amino, and reacting one mol of the so-obtained amine with one mol of cyanuric chloride at 010 C. and one mol of the resultant condensation product at 2050 C. with one mol of a base of formula V H and finally at 80100 C. with one mol of a base of formula ZH. The order in which the bases of formulae XH, YH, ZH and V-H- are brought into reaction can be varied as desired.

The compounds as thus prepared can be isolated by salting out, precipitation with acid, or by evaporation of the reaction mixture.

Particularly suitable compounds are for example those in the molecule of which the amino groups X, Y and Z are the radicals of primary aliphatic amines such asmethylamine, ethylamine',propy1amine, isop'ropylamine, butylamine, isobutylamine, ethanolamine, isopropanolamine, 'yhydroxypropylamine, fl-cyanoethylamine, ,B-cyanopropylamine, ,B-methoxyethylamine, etc., the radicals of secondary aliphatic amines such as dimethylamine, diethylamine, dipropylamine, dibutylamine, diethanolamine, methyl-(flhydroxyethyD-amine, ethyl-(,B-hydroxyethyl)-amine, diisopropanolamine, dibutanolamine, etc., the radicals of heterocyclic amines such as morpholine, piperidine, pyrrolidine, etc., the radicals of primary and secondary aromatic amines such as aniline, oand p-anisidine, chloraniline, toluidines, anilinesulfonic acids such as metanilic acid, orthanilic acid and sulfanilic acid, anisidinesulfonic acids, toluidinesulfonic acids, anilinedisulfonic acids, as well as the corresponding sulfona-Inides of the enumerated sulfonic acids, also the radicals of aliphatic aminosulfonic acids, such as amino-methanesulfonic acid, taurine, methyltaurine, etc., and also the NH group itself. In this connection, R (referring to Formula 1, supra) is H, a lower alkyl group such as methyl, ethyl, etc., a cyanoalkyl group such as e-cyanoethyl, ,B-cyanopropyl, etc., or preferably an oxyalkyl group such asB-hydroxyethyl, ft-hydroxypropyl, 'y-hydroxypropyl, ,B-methoxyethyl, ,B-ethoxyethyl, etc., and those in the molecule of which the aminogroups X or X, Y and Z are identical with V.

The amines which contain the R Ih-N-(CHzh-C l \CEN group in the molecule are readily prepared in per se known manner; thus e.g. those wherein n is 1 are prepared from bases R -NH and acrylonitrile or methacrylonitrile, and those wherein n is zero are prepared from bases R -NH and hydroxycarboxylic acid nitriles or from a-aminoalkylsulfonic acids and alkali metal cyanides.

Although the brighteners of the invention are especially useful in the size press, as already indicated, and in this respect alone are markedly distinguished from similarly constructed brighteners which do not contain the cyanoalkyl group in the molecule thereof, the new brighteners are also useful in other applications. Thus, they are valuable products for the optical brighening of paper pulp in the Hollander, and they are also useful for the White toning of textiles from cotton, viscose, nylon, wool, etc.

The new brighteners may be employed individually or in admixture and also in combination with other brighteners and with finishing agents, e.g. synthetic resin finishes on the basis of carbarnide-formaldehyde precondensates, such as dimethylolurea or methylolmelamines or polymers of the vinyl, acrylic and styrene series, and also in the presence of surface-active materials such as washing and wetting agents. They can also be added to spinning masses.

In comparison with known brighteners which contain no cyanoalkyl group in the molecule, they present the following advantages: they are better soluble, more resistant to acid, faster to light and have superior levelling capacity.

In the following examples, setting forth presently preferred exemplary embodiments of the invention, the parts are parts by weight, the percentages are by weight, and the temperatures are in degrees centigrade.

Example] for 2 hours, the pH being maintained at between 6.5 and 7.0 by the addition of a solution of 40 parts of sodium hydroxide in 360 parts of water. A solution of 74 parts of B-cyanoethylamine in 150 parts of water is then again added, and the mixture heated to 100 for 5 hours, whereby the acetone is distilled ofi; the HCl liberated during the reaction is continuously neutralized by the gradual addition of 400 parts of 10% aqueous sodium hydroxide solution.

The reaction mixture is diluted to 10,000 parts with Water and is then acidified at 50 by the addition of 240 parts of hydrochloric acid 1:1 (1 part by volume of concentrated hydrochloric acid-l-l part by volume of water), after which the precipitated acid is filtered off with suction. This is then suspended in 2500 parts of water at 50" and is neutralized by the addition of 400 parts of 10% aqueous sodium hydroxide solution, the resultant solution filtered and evaporated to dryness under reduced pressure.

The so-obtained sodium 4,4-bis-(Z-B-cyanoethylamino- 4 [3 cyanoethylamino 1,3,5 triazyl (6) amino stilbene-2,2'-disulfona.te is a bright yellow powder which is readily soluble in water. It is a valuable brightener, which imparts a beautiful light-fast brightening to paper, when applied to the pulp or by surface treatment. The product is stable to acids and to aluminum sulfate. Applied to paper, it is several times more effective than the corresponding sodium 4,4-bis-(2,4-diamino-l,3,5-triazyl- (6)-amino)-sti1bene-2,2-disulfonate which contains no cyanoethyl group in the molecule.

A brightener of like properties is obtained when, in the foregoing, the 74 parts of fi-cyanoethylamine reacted at 95100, are replaced by 129 parts of fi,fl-dicyanodiethylamine.

Example 2 A solution of 120 parts of fi-cyanoethyl-(fi'-hydroxyethyl)-amine in 200 parts of water is stirred at 20 into a suspension, prepared according to Example 1, of 355 parts of sodium 4,4-bis-(2,4-dichloro-l,3,5-triazyl-(6)- amino)-stilbene-2,2'-disulfonate in 2000 parts of water and 800 parts of acetone. The mixture is warmed to 4045 for 4 hours with constant neutralization to a pH of 7 by means of a total of 400 parts of 10% aqueous sodium hydroxide solution. T hereupon a solution of 120 parts of fi-cyanoethyl-(,6'-hydroxyethyl)-amine in 200 parts of water is again added, the mixture is heated to '95100 under a descending condenser, while gradually dropping in 400 parts of 10% aqueous sodium hydroxide solution at such a rate that the pH remains at 7.5 to 8.5. The clear reaction solution is diluted to 3500 parts with water. 525 parts of sodium chloride are then added at 60, the precipitated product suction-filtered off at 20 and dried under reduced pressure.

The said product is a valuable brightener, especially for paper, and is stable to acid as well as aluminum sulfate. Usedin the size press on sized paper at 2 grams per liter at pH 6, it produces very good brightening. In sharp contrast, the corresponding compound which, instead of the fi-cyanoethyl-(fi-hydroxyethyl)-amino groups, contains only B-hydroxyethylamino groups, cannot be applied to this use, since it does not brighten the paper at all but imparts a greenish discoloration thereto.

The ,B-cyanoethyl-(B-hydroxyethyl)-amine, added at 20, can in the precedingly described process of this example be replaced by 114 parts of ,B-cyanoethyl-(fi-hydroxypropyl)-amine, and the subsequently added firstmentioned amine by parts of diethanolamine, thereby yielding a brightener of properties like those of the initially-described product.

Example 3 A solution of 173 parts of metanilic acid in 500 parts of water, neutralized torpH 7.5 with sodium carbonate, is stirred at 10 in the course of 10 minutes into a suspension of 355 parts of sodium 4,4'-bis-(2,4dichloro-1,3,5- triazyl-(6)-amino)-stilbene-2,2-disulfonate in 2000 parts of water and 800 parts of acetone. The mixture is heated to 40 and kept at this temperature for 2 hours. Care is taken by the dropwise addition of 200 parts of 20% aqueous sodium hydroxide solution that the liberated hydrochloric acid is constantly neutralized and the pH value of the reaction mixture remains between 6 and 7.

114 parts of B-cyanoethyl-(fi'-hydroxyethyl)-arnine are then added and the solution is heated to 100 under a descending condenser for hours, during which time 200 parts of 20% aqueous sodium hydroxide solution are added dropwise at such rate that pH remains between 7.5 and 8.5. The solution is then filtered and evaporated to dryness under reduced pressure.

The so-obtained bright yellow powder, which consists of about 75% sodium 4,4-bis-(2-m-sulfophenylamino-4- ,8 cyanoethyl ,8 hydroxyethylamino 1,3,5 triazyl- (6)-amino) -stilbene-2,2'-disulfonate and about 25% sodium chloride, can be purified by dissolution in the ten-fold quantity of hot water and salting out with 15% aqueous sodium chloride solution.

The product is a valuable brightening agent, especially for paper. It can be used in the Hollander, in the immersion or spraying process. Particularly in the size press application, with sized paper having a surface pH of about 6, it is greatly superior to the corresponding compound which contains in its molecule e.g. a hydrogen atom in place of the cyanoethyl group.

A brightener of like properties as that produced according to the present example is obtained if, in the foregoing, the 114 parts of B-cyanoethyl-(B-hydroxyethyl)-amine are replaced by 126 parts of fi-cyanoethyl-(,6'-hydroxypropyl) amine, or if the metanilic acid is replaced by the same quantity of sulfanilic acid.

Examples 4 to 21 355 parts (0.5 mol) of sodium 4,4'-bs-(2,4-dichloro- 1,3 ,5 -triazyl- 6 -amino) -stilbene-2,2'-disulfonate prepared from 1 mol of cyanuric chloride and 0.5 mol of 4,4'-diaminostilbene-2,2-disulfonic acid are reacted, in the manner described in Example 3, at 35-45 with one mol of the amine XH and at 95-100 with one mol of the amine XH, the specific X-H and XH amines being those set forth in the table which follows:

pvl) -am ine. V N'B-evanoethyl-pmethoxyaniline.

metanilic acid ortham'lic acid sulfanilie acid 2-arrino-1-methylbenzene- 5-sulfonic acid.

Z-amino-l-methoxybenzene- 4-sul-onic acid.

metanilic a N-methyltaurina--- metanilic acid sulianilic acid fl-cyanoethylam ine. ethy1-( dcyanoprop h -arn ine. B,B-die vanod ipropylan ine. B cyano thxl 3 hydroxy prgpyl) amine.

B cyanoethyl (B methoxy ethyl) -am ine.

cyanomethylamine.

a-cyanoethylam ine.

cyanomethyl (fi hydroxyethyl) amine.

Example 22 A solution of 770 parts of sodium 4'-amino-4-(2"-msulfophenylamino 4 morpholino 1",3",5 triazyl- (6") )-amino stilbene-2,2-disulfonate and 53 parts of calcined sodium carbonate in 10000 parts of water is stirred dropwise at 0-5 in the course of half an hour into a suspension of 185 parts of cyanuric chloride in 800 parts of acetone and 2000 parts of ice water (cf. Example 1).

At the end of fifteen minutes, primary aromatic amino groups are no longer detectable. 128 parts of ,B-cyanoethyl-(fi'-hydroxypropyl)-amine in solution in 300 parts of water are then added, after which the mixture is heated to 45 for 3 hours while adding a total of 800 parts of 5% aqueous sodium hydroxide solution. 128 parts of fi-cyanoethyl- (,6-hydroxypropyl)-amine in solution in 300 parts of water are then again added, the temperature raised to and, at this temperature, 800 parts of 5% aqueous sodium hydroxide solution added dropwise in the course of 2 hours. The resultant mixture is stirred for 2 hours at 95l00, after which it is evaporated to dryness in a spray dryer.

The so-obtained brightener which, apart from a small quantity of sodium chloride, consists of sodium 4-(2"'- ,8 cyanoethyl 13 hydroxypropyl amino 4" 8 cyanoethyl 8' hydroxypropylamino 1"',3",5"' triazyl- (6"') amino 4 (2,2' m sulfophenylamino 4"- morpholino 1",3",5" triazyl (6") aminostilbene- 2,2-disulfonate, and is especially suitable for the brightening of paper.

The starting compound can be prepared in known manner from one mol each of 4-riitro-4-aminostilbene- 2,2'-disulfonic acid, cyanuric chloride, metanilic acid and morpholine, with reduction of the nitro group.

The [3 cyanoethyl (,B hydroxypropyl) amine (128 parts) reacted at 45 can be replaced by 114 parts of fl-cyanoethyl-( 3-hydroxyethyl)-amine, and the second portion of the first-named amine by 87 parts of morpholine, while otherwise proceeding as set forth in this eX- ample, whereby a brightener with properties similar to those of the product described in the first paragraph are obtained.

Example 23 Undyed paper pulp of bleached sulfite cellulose is beaten in a Hollander at a density of 2.5%. To the resultant mass, there is added 0.1% (relative to the dry weight) of the first brightener described in Example 1, in solution in a small quantity of water, and beating continued for 15 more minutes. Then 2% (relative to the weight of the dry fiber) of colophony as 2% rosin milk (Harzmilch) and 3% (also relative to the weight of the dry fiber) of aluminum sulfate as a 10% aqueous solution are added. The pulp is diluted with water to a material density of 0.5% and paper sheets poured from this mass. These sheets, after drying, are strongly brightened. The corresponding compound which contains an NH group in the molecule in lieu of the cyanoethylamino group is unsuitable for the indicated purpose.

The compounds of Examples 2 to 22 can be used in like manner.

Example 24 A dry paper web, sized with 2% (relative to the weight of the dry fiber) rosin milk and 3% aluminum sulfate and having a surface pH of 4.5, is passed through a Foulard in which, for about 3 seconds, it is immersed in an aqueous solution which contains 50 grams per liter of dextrine and 1 gram of the brightener of Example 13 and has a pH of 6, and is then squeezed down to about 150%. The paper, after being dried at is distinctly brightened. A like brightening eifect can be obtained with the brighteners disclosed in Examples 1 to 12 and 14 to 19.

Example 25 A fabric of bleached cotton poplin is treated, at a goods-to-liquor ratio of 1:30 and at 40, for 30 minutes, in a bath containing, per liter, 5 milligrams of the brightener first-described in Example 3 and 5 grams of calcined Glaubers salt. After being rinsed and dried, the fabric is distinctly brightened.

Example 26 Undyed raw woolen yarn, reinforced with nylon,

is moved about for 30 minutes at 70 at a goods-toliquor ratio of 1:4, in a bath containing per liter 50 milligrams of the first-described brightened of Example 2 and 1 gram of glacial acetic acid. The yarn, after drying, has a distinctly brightened appearance.

Example 27 A web of undyed cotton cretonne is impregnated in a Foulard with a solution which contains, per liter, 150 grams of a urea-formaldehyde precondensate, 2 grams of ammonium sulfate and 0.05 gram of the brightener of Example 16, then squeezed down to 100%, pre-dried at 80, and thereafter aftercondensed at 120. The thus crease-proofed fabric is distinctly brightened.

A like brightening effect is achieved with the brighteners of Examples 1 to 15 and 17 to 22.

For the sake of completeness, it is noteworthy that no significance is attached to the fact that the foregoing illustrative examples happen to employ the compounds I in the form of the di-sodium salts. M (see the formula of claim 3) represents any cation, including H, but preferably-and solely because of easy accessibility of the correspondin compoundsalkali metal cations. Here again, the preferred cation M is Na, although the K salts are essentially equivalent to the Na salts.

Having thus disclosed the invention, What is claimed is:

1. A water-soluble compound of the formula wherein the substituents V, X, Y and Z are amine radi- NEG-CHr-CHz I I] I ll SO Na o NEG-mam I IHQSOaNa /N v NC/ CAHQCHECHQNH-G o-N I II I ll N r 1 N cals each of which is attached by its amino nitrogen atom to the respective triazine ring, and at least one of which substituents has the formula -N GEN R is a member selected from the group consisting of hydrogen and methyl; R is a member selected from the group consisting of hydrogen, alkyl, hydroxyalkyl, cyanoalkyl and alkoxyalkyl, each of the last four members having at most 4 carbon atoms; n is an integer ranging from 0 to 1; and M is a cation selected from the group consisting of hydrogen and alkali metal cations; remaining substituents being amine radicals selected from the group consisting of NH unsubstituted primary and secondary lower alkyl-amino, hydroxy-lower alkyl-amino, cyano-lower alkyl-amino, sulfo-lower alkyl-amino, alkoxyalkyl-arnino having a total of 3 to 4 carbon atoms, morpholino, piperidino, pyrrolidino, anilino, chloroanilino, toluidino, oand p-anisidino, sulfoanilino, sulfoanisidino, sulfotoluidino, sulfonamido-anilino, sulfonamidoanisidino and sulfonamido-toluidino.

2. Sodium 4,4 bis-(2-,8-cyanoethylamino-4-B-cyanoethylamino 1,3,5 triazyl (6) amino) stilhene 2,2- disulfonate.

3. Sodium 4,4'-bis-(Z-B,B'-dicyanodiethylamino-4-,8,B'- dicyanodiethylamino 1,3,5 triazyl-(6)-amino)-stilbene- 2,2-disulfonate.

4. Sodium 4,4-bis-[Z-B-cyanoethyl-(,B-hydroxypropyD- amino 4 B-cyanoethyl-(fi-hydroxypropyl)-amino-1,3,5- triazyl- (6 -amino] -stilbene-2,2-disulfonate.

5. A compound of the formula CHr-CHPCEN 6. A compound of the formula N CHzCH -CEN so Na NaO s H0 a a OH 1 l SOaNfl some 7. A compound of the formula NEG-CHz-CH: N N CHz-CHa-CEN /N(|1 (J-NH CH=CH NIH-(l3 HO-CH -CH; N N I N N CHa-CHz-OH SOaNa NaO S C 1 Q -Q I s oaNa K a HOCHz-CH: N N

CH1CHr-0H 8. A compound of the formula CHPCHPCEN SOaNa NaO S 9. A compound of the formula SOzNa NaOaS /N I /N\ /CHa-CH2CEN s10 I T\ N\ N CHz-CHa-OH 3N3 C CHrCH: ]J/0H3C= I \CHPCHQ r-CH:

References Cited in the file of this patent UNITED STATES PATENTS 2,376,743 Wendt May 22, 1945 2,618,636 Williams et al Nov. 18, 1952 2,666,052 Williams et a1 Jan. 12, 1954 2,762,801 Hausermann Sept. 11, 1956 2,766,239 Fleck Oct. 9, 1956 2,901,477 Siegel et al. Aug. 25, 1959 2,945,762 Carroll et al. July 19, 1960 2,956,898 Fleck Oct. 18, 1960 FOREIGN PATENTS 541,278 Canada May 21, 1957 705,406 Great Britain Mar. 10, 1954 

1. A WATER-SOLUBLE COMPOUND OF THE FORMULA 